1. Field of the Invention
In general, this particular invention pertains to perforating material. Specifically, it is directed to a novel and improved process and apparatus for accomplishing such process whereby material, such as cigarette tipping paper, is perforated by laser beams for producing a multiplicity of apertures in the tipping material.
2. Description of the Prior Art
In the tobacco industry, it is rather common practice to perforate cigarette tipping paper in order to produce a plurality of openings therein. Such openings generally serve the purpose of controlling the main stream delivery of cigarette smoke constituents. By controlling the main stream of delivery of smoke constituents, such properties, as tar and nicotine levels, can be advantageously regulated. Should, however, the openings be irregularly and/or partially formed, such makes reasonably accurate control of the constituents more difficult to obtain. As a consequence thereof, the openings would fail to effectively perform in the manner intended. It will be recognized, of course, that if effective and accurate control of cigarette smoke constituents is to be accomplished, such openings should be accurately formed and spaced apart. Moreover, such accuracy is important from the standpoint of providing and maintaining the desired level of cigarette smoke constituents. For example, if smoke constituents exceed an amount represented by a manufacturer, such manufacturer might to subject to government sanctions. It will be appreciated, therefore, that there is an emphasis upon achieving the proper and accurate formation of openings in the tipping paper, since it, in turn, controls the main stream delivery of cigarette smoke constituents.
There are several known prior art approaches for perforating material, such as cigarette tipping paper. Such known perforating methods include use of mechanical pins, electrical sparks, and lasers. Of the foregoing methods, use of mechanical pins has been generally widely adopted throughout the industry for achieving such perforation. Essentially, mechanical pins serve to actually puncture or perforate the material they cooperate with. In actual practice, however, it has been commonly experienced that mechanical pins are relatively complicated and cumbersome in use. Another drawback encountered is that the pins are frequently subject to mechanical failure which results in no opening or perforation. Apart from the foregoing shortcomings, mechanical pins frequently do not cleanly perforate openings in the intended manner since, in many instances, what normally occurs is that the tipping paper being punctured by the pins actually tears. Such tearing results in ragged edges which have a tendency to close up the intended openings as the paper is wound in the usual manner. As can be appreciated from the foregoing brief description there are numerous disadvantages associated with the application of mechanical pins for perforating extremely small openings in the tipping paper. Accordingly, less than entirely satisfactory openinqs are provided.
As concerns the less widely used electric sparking technique, such serves to actually burn apertures in the paper. The significant disadvantages associated with this particular technique are a charred appearance produced about the periphery of the formed apertures and, in addition, irregularly formed apertures. Accordingly, there is a tendency for not only a non-aesthetic appearance but, also, non-uniformity in size and spacing of the apertures. Consequently, a less than effective means is provided to control the formation of apertures in the tipping paper so as to correspondingly more accurately control the main stream delivery of cigarette smoke constituents.
As previously observed, laser apparatus have been employed in a wide variety of situations for purposes of perforating numerous materials including cigarette tipping paper. Generally speaking, though, heretofore known approaches to perforate material, particularly in those situations where such material is continuously advanced in a predetermined path, are subject to several significant disadvantages. One example of such type of known laser technique is basically disclosed in U.S. Pat. No. 3,808,394. As therein described, a pulsating form of laser beam is directed towards a rotating mirror which, in turn, reflects the beam of laser energy towards an opening in an independently rotating drum. The laser beam serves to vaporize the material adjacent the opening for correspondingly forming an aperture in the advancing material. Such prior art approach, however, suffers from the shortcoming of requiring quite expensive electrical components to produce the pulsating energy necessary to perforate the material. Additionally, this particular approach is unable to effectively ensure uniformity of spacing of the holes because it does not compensate for varying rates of speed as the material is advanced since the drum is responsible for driving the material.
It is known in the laser field to form a plurality of perforations in a sheet of material through appropriately scanning a laser beam across the sheet. Normally, with such an approach the laser beam scans the material and is then stopped for purposes of accurately aligning the beam at the particular desired location so as to enable the beam to form a corresponding perforation. From the foregoing, it becomes evident that should a large number of perforations be formed in a mass production situation, such approach would be extremely time consuming and costly considering not only the amount of time involved but, also, the complex arrangement and expense of equipment necessary for performing the scanning and pulsing of the laser head in prescribed intervals of time.
One prior art attempt to partially overcome the above enumerated drawbacks associated with perforating a plurality of discrete apertures is through the utilization of a laser mask having a number of apertures through which a laser beam passes for forming corresponding perforations. By way of specific example, such a laser mask arrangement is disclosed in U.S. Pat. No. 3,742,182. In the above referenced patent, it is described that by reason of such mask a faster technique is developed since the laser beam can be scanned across the holes of the mask without having to stop for each hole and be accurately aligned in the desired position. Nevertheless, there are significant disadvantages associated with this particular technique inasmuch as expensive and complicated mechanical arrangements must also be utilized to achieve the relative scanning movement of the laser with accuracy. Furthermore, the foregoing category of laser perforating arrangement is unable, without extremely expensive control systems, to provide uniformity in the spacing of perforations should the speed of the relatively moving material to the mask vary during a particular time span. Accordingly, the preceding described system is less than satisfactory for many applications, particularly in high speed applications requiring precise alignment and formation of perforations in the material regardless of fluctuations and interruption in the continuous advancement of material.
While, as previously noted, there have been efforts in the tobacco industry to utilize laser beams for purposes of perforating cigarette paper and, in particular, tipping paper, the heretofore known attempts have failed to provide a highly accurate, reliable and inexpensive solution. Several reasons contribute to such lack of success. Foremost among the problems is the fact that tipping paper is normally produced in rather wide parent rolls. Frequently, such rolls are about 44 inches in width, however, in practice the width depends upon the width of the press the paper is printed on. Typically, though such parent rolls are exceedingly wide especially in comparison to the width of the conventional bobbins cut therefrom. The present practice in the art is to have the tipping paper initially perforated by virtue of mechanical pins and then subsequently slit into approximately sixteen bobbins, with each bobbin containing a sufficient width for two cigarette tips. From a consideration of the preceding, it will be appreciated that should conventional laser perforating methods and apparatuses be applied for obtaining two sets of perforations in each bobbin, the equivalent of 32 cigarettes, a minimum of 32 laser beams would be required. If it were desired to have multiple rows in each cigarette tip, then 64 laser beams would be necessitated. Moreover, in such a situation the beams must be precisely aligned and in certain circumstances the beams would be spaced as close as 1 mm.
Apart from the enormously complicated engineering problems which undoubtedly would be encountered in installing so many laser heads and in properly aligning the laser beams for perforating, given the state of the art in perforating and slitting parent rolls of tipping paper, the costs factors involved would also result in a process and mechanical arrangement unacceptable for commercial utilization.
Additionally, should a laser beam be scanned across the tipping paper and pulsed in order to achieve perforations of the cigarette tipping paper, the attendant costs would also be commercially unreasonable.
Moreover, another of the disadvantages associated with the application of laser beams to advancing material is that laser pulsing is normally established for a given particular speed. Therefore, should variations occur in the speed of the advancing material, such as during the ordinary start-up and shut-down speeds experienced in many applications, the standard types of aforenoted laser arrangements would be unable to, without expensive and relatively sophisticated techniques, successfully maintain the desired uniformity of perforation spacing. In regard to cigarette tipping paper with about 3000 meters of such paper normally being started and stopped, the tendency for non-uniformity of spacing is significant. Accordingly, a substantial quantity of paper would not have the apertures uniformly spaced.
Finally, whereas the use of a mask can eliminate the problems associated with scanning the laser head or pulsing the laser beam, there remains the problem of driving the mask and the material together uniformly at varying speeds.
As can be appreciated from the foregoing general description relating to known methods and apparatuses for use in perforating paper, and, in particular, tipping paper for cigarettes, none have been able to successfully, economically and with uniformity perforate paper through the use of laser beams.